a UDERZA Unit, Mechanical Department, Faculty of Technology, University of Eloued, 39000 Eloued, Algeria.

b Institute of Sciences, University Center of Tipaza, Algeria.

c Ecole Normale Superieure de Ouargla 30000 Algeria.

d University of Bordj Bou Arreridj, Bordj Bou Arreridj34030, Algeria

In this work, we carried out a detailed ab initio investigation of the chalcopyrite-type semiconductors AuAlS₂ and AuInS₂, addressing their structural, electronic, optical, elastic, and thermoelectric behavior. The calculations were performed using the full- potential linearized augmented plane wave (FP-LAPW) scheme within the density functional theory (DFT) framework. The optimized lattice constants (a, c) and the internal parameter (u) were found to be consistent with reported experimental and theoretical data.

Band structure calculations confirmed the presence of direct band gaps in both materials, a property favorable for photovoltaic and optoelectronic applications. The optical spectra indicated strong absorption within the visible range, supporting their effectiveness as solar absorbers. Elastic constants satisfied the mechanical stability requirements, validating the robustness of the compounds. Moreover, preliminary thermoelectric analysis revealed promising energy-conversion capability, underlining their potential contribution to sustainable energy technologies